I have recently gone back to an earlier backed up image for other reasons, and haven't looked at telephony with this one yet, but I am almost certain I had that firewall rule in there, but it was tcp, not udp (would help if I knew the difference! *googles*). Hmm, does it make much difference? Of course I will try again with the firewall rule you mentioned. FYI currently I have this...

I tried to get my phones to where they were before, but something different is happening this time, can't get the line to register again, says "Request Sent", nothing else is happening. Same snapshot, same installation, same upgrade level.

I think the problem may lie in /etc/asterisk/asterisk.conf. I can't remember who sent me theirs originally on IRC, but that one worked.